For improving light emitting efficiency and photovoltaic efficiency in an electronic device such as a light-emitting device containing organic compounds as materials for a light-emitting layer and a photovoltaic cell containing organic compounds as materials for a charge separating layer, an electron injection characteristic is required to be improved in such electronic device.
To improve the electron injection characteristic, (1) a method for forming a cathode by depositing a metal layer having a small work function further on a metal layer having a large work function such as aluminum using a deposition method; (2) a method for forming a cathode by depositing an alloy layer in which the alloy is made of a metal having a large work function and a metal having a small work function using a deposition method; and (3) a method for forming an electron injection layer made of a material such as an alkali metal compound and an alkali earth metal compound stacked by a deposition method on a cathode made of a metal layer formed by a deposition method are known.
When a deposition method is used for forming a metal layer or an alloy layer, a batch process based on a vacuum system is required. As a result, problems of reduction in yield caused by losing continuity of the manufacturing process and increase in manufacturing cost arise.
To solve these problems, a light-emitting device in which an electron injection layer, a cathode, and the like are formed by a coating method that forms a coating film using a coating solution has been reported (Patent Document 1 and Non Patent Document 1).